1. Field of the Invention
The present invention relates generally to apparatus for inhibiting the flow of fluid between two confronting surfaces and, more particularly, to such apparatus that includes a flexible sealing device.
2. Description of the Prior Art
Lip seals are commonly used to inhibit the flow of fluid to or from the interior of such pressure chambers as sterilizer chambers. Lip seals operate to seal a chamber opening when a pressure differential of a minimum predetermined amount is present across the seal. The existence of the pressure differential causes the seal to be forced against one of the surfaces between which it is disposed when the chamber is closed to seal the opening.
Generally, a lip seal includes a base member which extends along and is mounted to either the end ring or the door of the sterilizer. One type of lip seal--a double lip seal--includes a pair of flexible members extending from the base member along its entire length. The base member and the flexible members are adapted to make contact with the end ring of the sterilizer chamber and the door when the door is in its closed position in which it confronts the end ring. It is common for the base member to be mounted to the door and the free ends of the flexible members to be in contact with the end ring when the door is in its closed position. In such a configuration, the flexible members and the end ring define an enclosed space.
To ensure proper operation of the sterilizer closure--that is to ensure that the flow of fluid to and from the sterilizer chamber is inhibited sufficiently--a force must be exerted on either the interior lip--the lip that is exposed to the fluid within the chamber--if the chamber is under positive pressure, or the exterior lip--the lip that is exposed to the atmosphere--if the chamber is under a vacuum, of a magnitude sufficient to force the lip against the end ring and prevent fluid flow between the lip and the end ring.
Sterilizers which use a compression seal to seal the opening of the sterilizer chamber must include expensive and mechanically complicated equipment for compressing the seal between the sterilizer door and the end ring. Sterilizers which use a lip seal need not include such equipment since the lip seal need not be compressed between the door and the end ring to operate properly.
However, it has not been possible to use lip seals to effectively seal some types of chambers. For example, a washer sterilizer must contain a substantial amount of water in an otherwise unpressurized chamber. Lip seals have been unsuitable for use with washer sterilizers because the water in the vicinity of the water line within the chamber cannot establish a pressure differential across the seal of a magnitude that is sufficient to cause proper seating of the seal against the end ring; thus, some water escapes from the chamber. Accordingly, compression seals are commonly used to seal the opening of washer sterilizers.
Further, although double lip seals can be used advantageously with chambers which operate under positive gaseous pressure or a vacuum, some leakage of gas from the chamber may occur when the chamber is brought from a state of substantially zero pressure to a positive gaseous pressure by the introduction of gas to the chamber. Since some gases used in sterilizer chambers can pose a health hazard to hospital personnel who are exposed to them, it is desirable to avoid such gas leakage.